Composite positive active material, method of preparing the same, positive electrode including the composite positive active material, and lithium battery including the positive electrode

ABSTRACT

A composite positive active material includes: a composite including a first metal oxide represented by Formula 1 and having a layered structure, and a second metal oxide having at least one crystal structure selected from a layer structure, a perovskite structure, a rock salt structure, and a spinel structure, wherein a content of the second metal oxide is greater than 0 and equal to or less than 0.2 moles, per mole of the composite, 
       LiNi x M 1   1-x O 2-e M 2   e   Formula 1
 
     wherein, in Formula 1, M 1  is at least one element selected from Group 4 to Group 14 of the Periodic Table of the Elements; M a  is at least one element selected from F, S, Cl, and Br; 0.7≦x&lt;1; and 0≦e&lt;1. Also, a positive electrode including the composite positive active material, and a lithium battery including the positive electrode.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of and priority to Korean PatentApplication No. 10-2015-0181856, filed on Dec. 18, 2015, in the KoreanIntellectual Property Office, and all the benefits accruing therefromunder 35 U.S.C. §119, the content of which is incorporated herein in itsentirety by reference.

BACKGROUND

1. Field

The present disclosure relates to a composite active material, methodsof preparing the same, a positive electrode including the compositeactive material, and a lithium battery including the positive electrode.

2. Description of the Related Art

Along with the use of lithium batteries as power sources for portableelectronic devices and vehicles, vigorous research is in progress toimprove the capacity of lithium batteries. The trends towardmultifunctional and higher functional devices are increasing demand forsmaller, lighter, and higher-voltage lithium batteries for use as powersources of such devices.

To implement lithium batteries satisfying such demands, there is a needfor positive active materials with improved lifespan and capacitycharacteristics, and suppressed reduction in voltage characteristicseven under repeated charging and discharging.

SUMMARY

Provided is a composite positive active material that is structurallystable under repeated charging and discharging, and a method ofpreparing the positive active material.

Provided is a positive electrode including the composite positive activematerial.

Provided is a lithium battery including the positive electrode.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

According to an aspect of an embodiment, a composite positive activematerial includes: a composite including a first metal oxide representedby Formula 1 and having a layered structure, and a second metal oxidehaving at least one crystal structure selected from a layered structure,a perovskite structure, a rock salt structure, and a spinel structure,wherein a content of the second metal oxide is greater than 0 and equalto or less than 0.2 moles, per mole of the composite,

LiNi_(x)M¹ _(1-x)O_(2-e)M′_(e)  Formula 1

wherein, in Formula 1, M¹ is at least one element selected from Group 4to Group 14 element of the Periodic Table of the Elements; M^(a) is atleast one element selected from F, S, Cl, and Br, 0.7≦x<1; and 0≦e<1.

According to an aspect of another embodiment, a method of preparing thecomposite positive active material includes: mixing a first metal oxideprecursor represented by Formula 13, a lithium precursor, and amanganese precursor to prepare a composition for forming a compositepositive active material; and thermally treating the composition forforming the composite positive active material to prepare the compositepositive active material:

Ni_(x)M¹ _(1-x)Q  Formula 13

wherein, in Formula 13,

M¹ is at least one element selected from Group 4 to Group 14 elements ofthe Periodic Table of the Elements,

Q is —OH, —CO₃, or —(C₂O₄)—, and

0.7≦x<1.

According to an aspect of another embodiment, a positive electrodeincludes the composite positive active material.

According to an aspect of another embodiment, a lithium battery includesthe positive electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of the embodiments, taken inconjunction with the accompanying drawings in which:

FIG. 1 is an exploded perspective view of a lithium battery according toan embodiment;

FIG. 2 is a graph of intensity (arbitrary units, a.u.) versusdiffraction angle (degrees two-theta, 2θ) and illustrates the results ofX-ray diffraction (XRD) analysis on composite positive active materialsof Preparation Examples 1 to 4 and a positive active material ofComparative Preparation Example 1;

FIG. 3 is an enlarged view of FIG. 2 illustrating the results of the XRDanalysis of the (003) plane;

FIG. 4A is an enlarged view of FIG. 2 illustrating the results of theXRD analysis of the (018) and (110) planes;

FIG. 4B is an enlarged view of FIG. 2 illustrating the results of theXRD analysis of the (110) plane in the composite positive activematerial of Preparation Example 4;

FIGS. 5A to 5E are scanning electron microscopic (SEM) images of thecomposite positive active materials of Preparation Examples 1 to 4 andthe positive active material of Comparative Preparation Example 1,respectively;

FIGS. 6A to 6C illustrate the results of electron probe microanalysis(EPMA) of the composite active material of Preparation Example 3 andshow the results of measuring the atomic ratio of nickel, cobalt andmanganese, respectively, while moving a probe of an electron probemicroanalyzer from a center of the composite positive active material ofPreparation Example 3 to a surface thereof;

FIG. 6D is a cross-sectional SEM image of the composite positive activematerial of Preparation Example 3;

FIGS. 7A to 7C illustrate the results of EPMA analysis of the positiveactive material of Comparative Preparation Example 1 and show theresults of measuring the atomic ratio of nickel, cobalt and manganese,respectively while moving a probe of an electron probe microanalyzerfrom the center of the positive active material of ComparativePreparation Example 1 to the surface thereof;

FIG. 7D is a cross-sectional SEM image of the composite positive activematerial of Comparative Preparation Example 1;

FIG. 8 is a graph of the amount of residual lithium (parts per million,ppm) versus the content of Li₂MnO₃ (mole fraction, based on a totalmoles of the composite positive active material) in the compositepositive active materials of Preparation Examples 1 to 3 and thepositive active material of Comparative Preparation Example 1; and

FIG. 9 is an HCl-titration graph of pH versus amount of 0.1 M HCl(milliliters, mL) used for measuring the amount of residual lithium inpositive active materials.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments, examples of whichare illustrated in the accompanying drawings, wherein like referencenumerals refer to like elements throughout. In this regard, the presentembodiments may have different forms and should not be construed asbeing limited to the descriptions set forth herein. Accordingly, theembodiments are merely described below, by referring to the figures, toexplain aspects. “Or means and/or.” As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items. Expressions such as “at least one of,” when preceding alist of elements, modify the entire list of elements and do not modifythe individual elements of the list.

It will be understood that when an element is referred to as being “on”another element, it can be directly on the other element or interveningelements may be present therebetween. In contrast, when an element isreferred to as being “directly on” another element, there are nointervening elements present.

It will be understood that, although the terms “first,” “second,”“third,” etc. may be used herein to describe various elements,components, regions, layers, and/or sections, these elements,components, regions, layers, and/or sections should not be limited bythese terms. These terms are only used to distinguish one element,component, region, layer, or section from another element, component,region, layer, or section. Thus, “a first element,” “component,”“region,” “layer,” or “section” discussed below could be termed a secondelement, component, region, layer, or section without departing from theteachings herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms, including “at least one,” unless the content clearly indicatesotherwise. “At least one” is not to be construed as limiting “a” or“an.” It will be further understood that the terms “comprises” and/or“comprising,” or “includes” and/or “including” when used in thisspecification, specify the presence of stated features, regions,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,regions, integers, steps, operations, elements, components, and/orgroups thereof.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

“About” or “approximately” as used herein is inclusive of the statedvalue and means within an acceptable range of deviation for theparticular value as determined by one of ordinary skill in the art,considering the measurement in question and the error associated withmeasurement of the particular quantity (i.e., the limitations of themeasurement system). For example, “about” can mean within one or morestandard deviations, or within ±30%, 20%, 10%, or 5% of the statedvalue.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Exemplary embodiments are described herein with reference to crosssection illustrations that are schematic illustrations of idealizedembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, embodiments described herein should not beconstrued as limited to the particular shapes of regions as illustratedherein but are to include deviations in shapes that result, for example,from manufacturing. For example, a region illustrated or described asflat may, typically, have rough and/or nonlinear features. Moreover,sharp angles that are illustrated may be rounded. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the precise shape of a region and are notintended to limit the scope of the present claims.

Hereinafter, embodiments of a composite positive active material, amethod of preparing the composite positive active material, a positiveelectrode including the composite positive active material, and alithium battery including the positive electrode will be disclosed ingreater detail.

According to an aspect of the present disclosure, a composite positiveactive material includes: a first metal oxide represented by Formula 1and having a layered structure; and a second metal oxide having at leastone crystalline structure selected from a layered structure, aperovskite structure, a rock salt structure, and a spinel structure,wherein the first metal oxide and the second metal oxide form acomposite, and wherein a content of the second metal oxide is greaterthan 0 and equal to or less than 0.2 moles, per mole of the composite,

LiNi_(x)M¹ _(1-x)O_(2-e)M^(a) _(e)  Formula 1

wherein, in Formula 1, M¹ is at least one element selected from Group 4to Group 14 elements of the Periodic Table of the Elements; M^(a) is atleast one element selected from F, S, Cl, and Br; 0.7≦x<1; and 0≦e<1.

As used herein, the terms “mole fraction” refers to a ratio of a mole ofthe first metal oxide or the second metal oxide with respect to a totalmoles of the composite positive active material.

In some embodiments, a mole fraction of the first metal oxide in thecomposite positive active material may be equal to or greater than 0.7and less than 1, equal to or greater than 0.8 and less than 1, or equalto or greater than 0.9 and less than 1.

If the mole fraction of the second metal oxide in the composite positiveactive material is greater than 0.2, the amount of residual lithium maybe reduced, but a lithium battery having a positive electrode includingthe composite positive active material may have deteriorated cellperformance, for example, in terms of capacity, conductivity, and celloutput.

To manufacture a lithium battery with high power output and highcapacity, there has been much research into the use of a lithium nickeloxide having high nickel content as a positive active material. However,the lithium nickel oxide having high nickel content may not havesufficient structural stability during charging and discharging,although it has improved capacity and power output characteristics, orsatisfactory lifetime characteristics due to high residual lithiumcontent. A battery including a lithium nickel oxide having a high nickelcontent may be prepared using a process of removing residual lithium.

Disclosed is a composite positive active material which can be used toprovide a lithium battery with improved lifetime characteristics byintroducing the second metal oxide as a secondary phase. While notwanting to be bound by theory, it is understood that inclusion of thesecond metal oxide as a secondary phase with the first metal oxide ofFormula 1, which comprises a high nickel content of about 0.7 mole ormore based on 1 mole of a total amount of a transition metal, provides acomposite having improved structural stability during charging anddischarging and may reduce the amount of residual lithium.

For example, the amount of lithium in the composite positive activematerial may be about 15,000 parts per million (ppm) or less, and insome embodiments, about 5,000 ppm to about 14600 ppm, and in some otherembodiments, about 9,810 ppm to about 14,571 ppm, or about 11,000 ppm toabout 13,000 ppm, based on a total amount of the composite positiveactive material. The amount of residual lithium is determined based on atotal of the amount of lithium hydroxide (LiOH) and the amount oflithium carbonate (Li₂CO₃). For example, the amount of lithium hydroxide(LiOH) may be from about 0.3 weight percent (wt %) to about 0.9 wt %,and in some embodiments, about 0.446 wt % to about 0.866 wt %, or about0.4 wt % to about 0.8 wt %. For example, the amount of lithium carbonate(Li₂CO₃) may be from about 0.45 wt % to about 0.6 wt %, for example,about 0.535 wt % to about 0.591 wt %, or about 0.5 wt % to about 0.59 wt%.

In Formula 1, M¹ may include at least one metal selected from manganese(Mn), vanadium (V), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni),zirconium (Zr), rhenium (Re), aluminum (Al), boron (B), germanium (Ge),ruthenium (Ru), tin (Sn), titanium (Ti), niobium (Nb), molybdenum (Mo),and platinum (Pt).

For example, the first metal oxide of Formula 1 may be a compoundrepresented by Formula 2.

LiNi_(x)Co_(y)Mn_(z)M³ _(c)O_(2-e)M² _(e)  Formula 2

In Formula 2, 0.7≦x≦0.99; 0≦y<1; 0<z<1; 0≦c<1; 0<x+y+z+c≦1; 0≦e<1; M³may be at least one selected from Group 4 to Group 14 elements of thePeriodic Table of the Elements; and M^(a) may be an anionic elementselected from F, S, Cl, and Br.

In some embodiments, in Formula 2, the amount of cobalt may be greaterthan the amount of manganese (i.e., y>z). When the amount of cobalt inFormula 2 is greater than the amount of manganese, a lithium batteryhaving a positive electrode including the composite positive activematerial may have further improved conductivity and capacitycharacteristics.

For example, the first metal oxide of Formula 1 may be a compoundrepresented by Formula 3

LiNi_(x)Co_(y)Mn_(z)O₂  Formula 3

In Formula 3, 0.7≦x≦0.99; 0<y<1; 0<z<1; and 0<x+y+z≦1.

In some embodiments, the second metal oxide having at least one crystalstructure selected from a layered structure, a perovskite structure, arock salt structure, and a spinel structure may be a compoundrepresented by Formula 4, a compound represented by Formula 5, acompound represented by Formula 6, or a compound represented by Formula7,

A₂M²O₃  Formula 4

AM²O₃  Formula 5

(A_(b)M² _(1-b))O  Formula 6

AM² ₂O₄  Formula 7

In Formulae 4 to 7, A may be at least one element selected from Group 1to Group 3 elements of the Periodic Table of the Elements; M² may be atleast one element selected from Group 2 to Group 16 elements and rareearth elements, and 0≦b≦1.

In Formulae 4 to 7, A may be at least one element selected from Li, Na,La, Sr, Ba, H, K, Ca, and Y; M² may be at least one element selectedfrom Al, Ga, Ge, Mg, Nb, Zn, Cd, Ti, Co, Ni, Mn, Ca, Si, Fe, Cu, Sn, V,B, P, Se, Bi, As, Zr, Re, Ru, Cr, Sr, Sc, and Y.

The compound represented by Formula 4 may be a compound having a layeredcrystalline structure, for example, Li₂MnO₃, Li₂TiO₃, Li₂SnO₃, Li₂ZrO₃,Li₂MoO₃, or Li₂RuO₃.

The compound represented by Formula 5 may be a compound having aperovskite crystalline structure, for example, a compound represented byFormula 8.

(A¹ _(1-a)A² _(a))M¹O  Formula 8

In Formula 8, A¹ may be at least one metal selected from La, Sr, Ba, Ce,Y, and Sc; A² may be at least one selected from Li, Na, Ca, Ag, K, Mg,and Cu; M¹ may be at least one selected from Mn, V, Cr, Fe, Co, Ni, Zr,Ti, Mg, Cu, Nb, Ta, Ru, W, and Sn; and 0<a≦0.3.

For example, the compound represented by Formula 8 may be LiMnO₃,(Li_(1-a)La_(a))MnO₃ (where 0<a≦0.3), (Li_(1-a)Sr_(a))MnO₃ (where0<a≦0.3), or (Li_(1-a),Ba_(a))MnO₃ (where 0<a≦0.3).

The compound represented by Formula 6 may be a compound having a rocksalt crystalline structure, for example, (Li_(b)Ni_(1-b))O,(Li_(b)CO_(1-b))O, (Li_(b)Fe_(1-b))O, (Li_(b)Cu_(1-b))O,(Li_(b)Zn_(1-b))O, (Li_(b)Ca_(1-b))O, (Li_(b)Sr_(1-b))O,(Li_(b)Mg_(1-b))O, or (Li_(b)Cr_(1-b))O, wherein 0≦b≦1.

The compound represented by Formula 7 may be a compound having a spinelcrystalline structure, for example, LiMn₂O₄, LiNi_(0.5)Mn_(1.5)O₄,LiCo_(0.5)Mn_(1.5)O₄, [Li][Co_(f)Ni_(g)Mn_(h)]₂O₄, or[Li][Cu_(c)Mn_(2-c)]₂O₄, wherein 0<c≦2, 0<f≦2; 0<g≦2, 0<h≦2; andf+g+h=2.

The first metal oxide having a layered structure in the compositepositive active material as described above may form a composite withthe second metal oxide. For example, the first metal oxide of thecomposite positive active material may include a crystal phase of theC2/m space group and a crystal phase of the R-3m space group. Thecrystal phase of the C2/m space group may be Li₂MO₃, and the crystalphase of the R-3m space group may be LiNi_(x)M¹ _(1-x)O_(2-e)M² _(e).

In some embodiments, the second metal oxide of the composite positiveactive material may be intermixed in the layered crystal structure ofthe first metal oxide.

In some embodiments, the composite positive active material may be atleast one selected from compounds represented by Formulae 9 to 12.

(1−a)LiNi_(x)M¹ _(1-x)O₂ .aA₂M²O₃  Formula 9

(1−a)LiNi_(x)M¹ _(1-x)O₂ .aAM²O₃  Formula 10

(1−a)LiNi_(x)M¹ _(1-x)O₂ .a(A_(b)M² _(1-b))O, and  Formula 11

(1−a)LiNi_(x)M¹ _(1-x)O₂ .aAM² ₂O₄  Formula 12

In Formulae 9 to 12, A may be at least one metal selected from Li, Na,La, Sr, Ba, H, K, Ca, and Y; M¹ may be at least one selected from Mn, V,Cr, Fe, Co, Zr, Ti, Mg, Cu, Nb, Ta, Ru, W, and Sn; M² may be at leastone selected from Al, Ga, Ge, Mg, Nb, Zn, Cd, Ti, Co, Ni, Mn, Ca, Si,Fe, Cu, Sn, V, B, P, Se, Bi, As, Zr, Re, Ru, Cr, Sr, Sc, Y, and a rareearth element; and 0<a≦0.2, 0<b≦1.

For example, the composite positive active material may be at least oneselected from compounds represented by Formulae 9-1 to 12-1.

(1−a)LiNi_(x)Co_(y)Mn_(z)O₂ .aLi₂MnO₃,  Formula 9-1

(1−a)LiNi_(x)Co_(y)Mn_(z)O₂ .aLiMnO₃,  Formula 10-1

(1−a)LiNi_(x)Co_(y)Mn_(z)O₂ .a(Li_(b)La_(1-b))MnO₃,  Formula 10-2

(1−a)LiNi_(x)Co_(y)Mn_(z)O₂ .a(Li_(b)Ni_(1-b))O,  Formula 11-1

(1−a)LiNi_(x)Co_(y)Mn_(z)O₂ .aLiMn₂O₄,  Formula 12-1

In Formulae 9-1 to 12-1, 0.7≦x≦0.99; 0<y≦0.3; 0<z≦0.3; x+y+z=1; 0<b≦1,and 0<a≦0.2.

In Formulae 9-1 to 12-1, LiNi_(x)Co_(y)Mn_(z)O₂ may beLiNi_(0.85)Co_(0.10)Mn_(0.05)O₂, LiNi_(0.8)Co_(0.1)Mn_(0.1)O₂,LiNi_(0.75)Co_(0.20)Mn_(0.05)O₂, or LiNi_(0.9)Co_(0.05)Mn_(0.05)O₂.

In some embodiments, the composite positive active material may be atleast one selected from 0.98LiNi_(0.85)Co_(0.10)Mn_(0.05)O₂.0.02Li₂MnO₃,0.95LiNi_(0.85)Co_(0.10)Mn_(0.05)O₂.0.05Li₂MnO₃,0.9LiNi_(0.85)Co_(0.10)Mn_(0.05)O₂.0.1Li₂MnO₃,0.8LiNi_(0.85)Co_(0.10)Mn_(0.05)O₂.0.2Li₂MnO₃,0.98LiNi_(0.8)Co_(0.1)Mn_(0.1)O₂.0.02Li₂MnO₃,0.95LiNi_(0.8)Co_(0.1)Mn_(0.1)O₂.0.05Li₂MnO₃,0.9LiNi_(0.8)Co_(0.1)Mn_(0.1)O₂.0.1Li₂MnO₃,0.8LiNi_(0.8)Co_(0.1)Mn_(0.1)O₂.0.2Li₂MnO₃,0.98LiNi_(0.75)Co_(0.20)Mn_(0.05)O₂.0.02Li₂MnO₃,0.95LiNi_(0.75)Co_(0.20)Mn_(0.05)O₂.0.05Li₂MnO₃,0.9LiNi_(0.75)Co_(0.20)Mn_(0.05)O₂.0.1Li₂MnO₃,0.8LiNi_(0.75)Co_(0.20)Mn_(0.05)O₂.0.2Li₂MnO₃,0.98LiNi_(0.9)Co_(0.05)Mn_(0.05)O₂.0.02Li₂MnO₃,0.95LiNi_(0.9)Co_(0.05)Mn_(0.05)O₂.0.05Li₂MnO₃,0.9LiNi_(0.9)Co_(0.05)Mn_(0.05)O₂.0.1Li₂MnO₃, and0.8LiNi_(0.8)Co_(0.05)Mn_(0.05)O₂.0.2Li₂MnO₃.

The composition of a composite positive active material may beidentified by X-ray diffraction analysis. In particular, a ratio of thefirst metal oxide of Formula 1 and the second metal oxide may beidentified based on an intensity ratio of peaks from the first metaloxide and the second metal oxide.

In some embodiments, the composite positive active material representedby Formula 9-1 may have a diffraction peak at a 2 theta (2θ) value ofabout 18.5° to about 19.0°, as measured by X-ray diffraction with Cu—Kαradiation. The diffraction peak at a 2θ value of about 18.5° to about19.0° may originate from the (003) plane of LiNi_(x)Co_(y)Mn_(z)O₂ inthe layered structure of the composite positive active material.

In some embodiments, in the composite positive active material, adiffraction angle 2θ of (003) plane peak of LiNi_(x)Co_(y)Mn_(z)O₂having maximum intensity may be shifted toward a lower angle, due to theintroduction of the secondary phase.

In some embodiments, the second metal oxide of the composite positiveactive material may be disposed on the surface of the composite positiveactive material. The second metal oxide may be disposed on an entiresurface of the composite positive active material, or may be disposed ona portion of the composite positive active material, such as about 1% toabout 99%, or about 10% to about 90%, or about 50% to about 80% of atotal surface area of the composite positive active material. Thus, thecomposite positive active material may have a surface including thesecond metal oxide. The composite positive active material may beprepared using a stepwise process, such as a melt impregnation process.The composite positive active material including the second metal oxidein a surface region thereof may exhibit an effect as if the surface ofthe first metal oxide is treated with the second metal oxide, and mayinclude a reduced amount of lithium on the surface of the compositepositive active material.

In some embodiments, the second metal oxide in the composite positiveactive material may have a concentration gradient. In some embodiments,the composite positive active material may have a concentration gradientof manganese (Mn). The composite positive active material may beprepared using a process in which the order of adding a manganeseprecursor is specifically selected to provide a concentration gradientof the second metal oxide and/or manganese.

In some embodiments, a half cell having a positive element including thecomposite positive active material and lithium metal as a counterelectrode may have an average discharge voltage of about 92.5% to about99.95% after a 50^(th) charging and discharging cycle, with respect tothe average discharge voltage after a 1^(st) charging and dischargingcycle. The composite positive active material may have a reduced averagedischarge voltage decay.

In some embodiments, the composite positive active material may have anaverage particle diameter of primary particles of about 100 nanometers(nm) to about 500 nm. For example, the composite positive activematerial may have an average particle diameter of primary particles ofabout 50 nm to about 1000 nm, or about 200 nm to about 400 nm, and anaverage particle diameter of secondary particles of about 0.5 micrometer(μm) to about 100 μm, about 1 μm to about 30 μm, or about 5 μm to about20 μm.

When the composite positive active material has an average particlediameter within any of these ranges, a lithium battery having improvedphysical characteristics may be obtained using the composite positiveactive material.

In some embodiments, the composite positive active material may have atap density of about 0.1 gram per cubic centimeter (g/cm³) to about 10g/cm³, about 0.5 gram per cubic centimeter (g/cm³) to about 3 g/cm³, orabout 1 gram per cubic centimeter (g/cm³) to about 2.5 g/cm³. A lithiumbattery having improved voltage and lifetime characteristics may beobtained using the composite positive active material having a tapdensity within this range.

The composite positive active material may further include a coatinglayer on the surface thereof. When the composite positive activematerial further includes a coating layer, a lithium battery with apositive electrode including the composite positive active material mayhave improved charge and discharge characteristics, lifespancharacteristics, and improved high-voltage characteristics.

In some embodiments, the coating layer may include at least one selectedfrom a conductive material, a metal oxide, and an inorganic fluoride.

The conductive material may be at least one selected from a carbonaceousmaterial, a conductive polymer, indium tin oxide, RuO₂, and ZnO.

The carbonaceous material may be crystalline carbon, amorphous carbon,or a mixture thereof. The crystalline carbon may be graphite, such asnatural graphite or artificial graphite, and may be amorphous, and maybe in a plate, flake, spherical or fibrous form. The amorphous carbonmay comprise at least one selected from a soft carbon (e.g., carbonsintered at a low temperature), hard carbon, meso-phase pitch carbide,sintered coke, graphene, carbon black, fullerene soot, carbon nanotube,and carbon fiber. However, examples of the crystalline carbon andamorphous carbon are not limited thereto. Any appropriate materialavailable in the art may be used.

Examples of the carbonaceous material may include carbon nanotubes,fullerene, graphene, and carbon fibers. Examples of the conductivepolymer may include at least one selected from polyaniline,polythiophene, and polypyrrole.

The metal oxide may include, for example, at least one selected fromsilica (SiO₂), alumina (Al₂O₃), zirconium oxide (ZrO₂), and titaniumoxide (TiO₂).

The inorganic fluoride may include at least one selected from AlF₃, CsF,KF, LiF, NaF, RbF, TiF, AgF, AgF₂, BaF₂, CaF₂, CuF₂, CdF₂, FeF₂, HgF₂,Hg₂F₂, MnF₂, MgF₂, NiF₂, PbF₂, SnF₂, SrF₂, XeF₂, ZnF₂, AlF₃, BF₃, BiF₃,CeF₃, CrF₃, DyF₃, EuF₃, GaF₃, GdF₃, Fe_(F3), HoF₃, InF₃, LaF₃, LuF₃,MnF₃, NdF₃, VOF₃, PrF₃, SbF₃, ScF₃, SmF₃, TbF₃, TiF₃, TmF₃, YF₃, YbF₃,TlF₃, CeF₄, GeF₄, HfF₄, SiF₄, SnF₄, TiF₄, VF₄, ZrF₄, NbF₅, SbF₅, TaF₅,BiF₅, MoF₆, ReF₆, SF₆, and WF₆.

In some embodiments, the coating layer may include at least one compoundof a coating element selected from oxide, hydroxide, oxyhydroxide,oxycarbonate, and hydroxycarbonate of the coating element. The compoundsfor the coating layer may be amorphous or crystalline. The coatingelement for the coating layer may comprise at least one selected fromSc, Y, Nb, Cr, Mo, W, Mn, Fe, B, In, C, Sb, La, Ce, Sm, Gd, Mg, Al, Co,K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, and Zr. The coating layer maybe formed by using any suitable method (e.g., a spray coating method, adipping method, or the like) that does not adversely affect the physicalproperties of the positive active material when a compound of thecoating element is used. Such methods of forming the coating layer wouldbe apparent to one of ordinary skill in the art, and the details ofwhich can be determined without undue experimentation, and thus, afurther detailed description thereof is omitted herein for clarity.

In an embodiment, the coating layer may be a continuous layer or adiscontinuous layer, and for example, may be in the form of an island.

Hereinafter, an embodiment of a method of preparing a composite positiveactive material is further disclosed.

The method of preparing a composite positive active material is notparticularly limited, and may be performed using any suitable method,for example, a co-precipitation method or a solid-phase method.

First, the co-precipitation method will be described. When a compositepositive active material is prepared using co-precipitation, thecomposite positive active material may have a uniform composition.

A first metal oxide precursor represented by Formula 13 may be mixedwith a lithium precursor and a manganese precursor to obtain a mixture,followed by thermally treating the mixture to obtain a compositepositive active material represented by Formula 4,

Ni_(x)M¹ _(1-x)Q  Formula 13

wherein in Formula 13, M¹ may be at least one element selected fromGroup 4 to Group 14 of the Periodic Table of the Elements; Q may be atleast one selected from —OH, —CO₃, and —(C₂O₄); and 0.7≦x<1. In anembodiment, —(C₂O₄)— is an oxalate ligand, i.e., —OC(═O)C(═O)O—.

The first metal oxide precursor represented by Formula 13 may be atleast one selected from a first metal hydroxide represented by Formula13a, a first metal carbonate represented by Formula 14, and a firstmetal oxalate represented by Formula 15 or Formula 16.

Ni_(x)M¹ _(1-x)OH  Formula 13a

Ni_(x)M¹ _(1-x)CO₃  Formula 14

Ni_(x)M¹ _(1-x)(OC(═O)C(═O)O)  Formula 15

Ni_(x)M¹ _(1-x)(C₂O₄)  [Formula 16]

In Formulae 13a, 14, 15, and 16, M¹ may be at least one element selectedfrom Group 4 to Group 14 of the periodic table of elements; and 0.7≦x<1.

Examples of the lithium precursor may include lithium carbonate(Li₂CO₃), lithium sulfate (Li₂SO₄), lithium nitrate (LiNO₃), and lithiumhydroxide (LiOH). The lithium precursor may be stoichiometrically mixedwith a metal compound represented by Formulae 13 to 16 to obtain acomposite positive active material having a composition represented byFormula 9-1, 10-1, 11-1, or 12-1.

A suitable example of the manganese precursor may ensure meltimpregnation into pores of the first metal oxide precursor through thethermal treatment without any remaining residue after the thermaltreatment. For example, the manganese precursor may be at least oneselected from manganese nitrate and manganese acetate. While not wantingto be bound by theory, using such a manganese precursor that does notgenerate any residue after the thermal treatment, unlike other manganeseprecursors, and ensures melt impregnation into pores of the first metaloxide precursor through the thermal treatment, may result in generationof a thermodynamically stable compound through reaction of lithium andmanganese. The resulting thermodynamically stable compound may havedifferent X-ray diffraction (XRD) characteristics from those of a firstmetal oxide including no secondary phase. Accordingly, the positiveactive material may include a reduced amount of lithium on the surfacethereof, for example, about 15,000 ppm or less of the composite positiveactive material.

The thermal treatment may be performed under an oxidizing gasatmosphere, for example, in air or oxygen at about 750° C. to about1200° C., and in some embodiments, about 800° C. to about 1000° C., orabout 850° C. to about 950° C. and in some other embodiments, at about900° C. When the thermal treatment temperature is within any of theseranges, a composite positive material including a reduced amount ofresidual lithium may be prepared.

The thermal treatment time may vary depending on thermal treatmenttemperature. For example, the thermal treatment time may be from about 5minutes to about 20 hours.

During the thermal treatment, the manganese precursor may be melted andimpregnated into pores of the first metal oxide precursor represented byFormula 13. The melt impregnation may enable the residual lithium in thefirst metal oxide precursor to react with manganese, thus to form astable phase. As a result, the amount of lithium on the surface of thecomposite positive active material may be remarkably reduced.

The compounds represented by Formulae 13 to 15, as examples of the firstmetal oxide precursor, may each be mixed with a nickel precursor, a M¹precursor, and a solvent to obtain a precursor mixture. The solvent maybe water, a C1 to C20 alcohol, or the like. For example, the alcohol maybe ethanol.

The amount of the solvent may be about 100 parts to about 4,000 parts byweight, about 200 parts to about 3,000 parts by weight, or about 400parts to about 2,000 parts by weight, with respect to 100 parts byweight of a total weight of the nickel precursor and M¹ precursor. Whenthe amount of the solvent is within this range, the exemplary firstmetal oxide precursors may each form a uniform mixture. The mixing maybe performed, for example, at about 20° C. to about 80° C., and in someembodiments, about 40° C. to about 60° C.

The M¹ precursor may be, for example, a M¹ carbonate, a M¹ sulfate, a M¹nitrate, or a M¹ chloride.

For example, the M¹ precursor may be a cobalt precursor or a manganeseprecursor. Non-limiting examples of the cobalt precursor are cobaltsulfate, cobalt nitrate, cobalt chloride, and cobalt acetate.Non-limiting examples of the manganese precursor are manganese sulfate,manganese nitrate, manganese chloride, manganese acetate, and manganesechloride.

The precursor mixture may then be mixed with a chelating agent and apH-adjusting agent (e.g., a precipitating agent), followed byco-precipitation reaction to obtain a precipitate. The precipitate maybe filtrated and thermally treated. The thermal treatment may beperformed at about 40° C. to about 110° C., and in some embodiments,about 40° C. to about 80° C. When the thermal treatment temperature iswithin any of these ranges, the co-precipitation reaction may haveimproved reactivity.

The chelating agent may regulate the rate of the co-precipitationreaction at which the precipitate is formed. Non-limiting examples ofthe chelating agent are ammonium hydroxide (NH₄OH), and citric acid. Theamount of the chelating agent may be the same as used in the art.

The pH-adjusting agent may control the pH of the precursor mixture to beabout pH 6 to 13, for example, about pH 10.5 to about 12.5, or about pH11 to about pH 12. Non-limiting examples of the pH-adjusting agent areammonium hydroxide, sodium hydroxide (NaOH), sodium carbonate (Na₂CO₃),and sodium oxalate (Na₂C₂O₄).

The first metal oxide precursor of Formula 13 may be, for example, acompound represented by Formula 14.

Ni_(x)Co_(y)Mn_(z)M³ _(c)OH  Formula 14

wherein, in Formula 14, 0.7≦x<1, 0<y≦0.3, 0<z≦0.3, 0≦c≦0.3, x+y+z+c=1,and M³ may be at least one element selected from Group 4 to Group 14 ofthe Periodic Table of the Elements.

The compound represented by Formula 14 may be, for example, a compoundrepresented by Formula 15.

Ni_(x)Co_(y)Mn_(z)OH  Formula 15

In Formula 15, 0.7≦x≦0.99, 0≦y≦0.3; 0≦z≦0.3, and x+y+z=1.

For example, the first metal oxide precursor may beLiNi_(0.85)Co_(0.10)Mn_(0.05)OH, LiNi_(0.8)Co_(0.1)Mn_(0.1)OH,LiNi_(0.75)Co_(0.20)Mn_(0.05)OH, or LiNi_(0.9)Co_(0.05)Mn_(0.05)OH.

In an embodiment, the composite positive active material may be preparedusing a suitable preparation method known in the art, such as asolid-phase method or a spray pyrolysis process, in addition to theabove-described co-precipitation method.

According to another aspect of the present disclosure, a positiveelectrode includes a composite positive active material.

According to another aspect of the present disclosure, a lithium batteryincludes the positive electrode.

A positive electrode according to an embodiment may be preparedaccording to the following method.

A positive active material, a binder, and a solvent may be mixedtogether to prepare a positive active material composition. A conductingagent may be further added to the positive active material composition.

The positive active material composition may be directly coated on ametal current collector and dried to form a positive electrode.Alternatively, the positive active material composition may be cast on aseparate support to form a film, which may then be separated from thesupport and then laminated on a metal current collector, to thereby forma positive electrode.

The positive active material may be a composite positive active materialaccording to any of the above-described embodiments.

The positive active material may further include a first positive activematerial which may be obtained commercially, in addition to thedisclosed composite positive active material.

The first positive active material may include at least one selectedfrom lithium cobalt oxide, lithium nickel cobalt manganese oxide,lithium nickel cobalt aluminum oxide, lithium iron phosphorus oxide, andlithium manganese oxide, but is not limited thereto. For example, thefirst positive active material may be any suitable positive activematerials available in the art.

For example, the first positive active material may comprise a compoundrepresented by the following formulae: Li_(a)A_(1-b)B′_(b)D₂ wherein0.90≦a≦1.8 and 0≦b≦0.5; Li_(a)E_(1-b)B′_(b)O_(2-c)D_(c) wherein0.90≦a≦1.8, 0≦b≦0.5, and 0≦c≦0.05; LiE_(2-b)B′_(b)O_(4-c)D_(c) wherein0≦b≦0.5, and 0≦c≦0.05; Li_(a)Ni_(1-b-c)Co_(b)B′_(c)D_(α) wherein0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, and 0<α≦2;Li_(a)Ni_(1-b-c)Co_(b)B′_(c)F_(α)F′_(α) wherein 0.90≦a≦1.8, 0≦b≦0.5,0≦c≦0.05, and 0<α<2; Li_(a)Ni_(1-b-c)Co_(b)B′_(c)O_(2-α)F′_(α) wherein0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, and 0<α<2;Li_(a)Ni_(1-b-c)Mn_(b)B′_(c)D_(α) wherein 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05,and 0<α≦2; Li_(a)Ni_(1-b-c)Mn_(b)B′_(c)O_(2-α)F′_(α) wherein 0.90≦a≦1.8,0≦b≦0.5, 0≦c≦0.05, and 0<α<2; Li_(a)Ni_(1-b-c)Mn_(b)B′_(c)O_(2-α)F′_(α)wherein 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, and 0<α<2;Li_(a)Ni_(b)E_(c)G_(d)O₂ wherein 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, and0.001≦d≦0.1; Li_(a)Ni_(b)Co_(c)Mn_(d)GeO₂ wherein 0.90≦a≦1.8, 0≦b≦0.9,0≦c≦0.5, 0≦d≦0.5, and 0.001≦e≦0.1; Li_(a)NiG_(b)O₂ wherein 0.90≦a≦1.8,and 0.001≦b≦0.1; Li_(a)CoG_(b)O₂ wherein 0.90≦a≦1.8 and 0.001≦b≦0.1;Li_(a)MnG_(b)O₂ wherein 0.90≦a≦1.8 and 0.001≦b≦0.1; Li_(a)Mn₂G_(b)O₄wherein 0.90≦a≦1.8 and 0.001≦b≦0.1; QO₂; QS₂; LiQS₂; V₂O₅; LiV₂O₅;LiI′O₂; LiNiVO₄; Li_((3-f))J₂(PO₄)₃ wherein 0≦f≦2; Li_((3-f))Fe₂(PO₄)₃wherein 0≦f≦2; and LiFePO₄.

In the formulae above, A may be nickel (Ni), cobalt (Co), manganese(Mn), or a combination thereof; B′ may be aluminum (Al), nickel (Ni),cobalt (Co), manganese (Mn), chromium (Cr), iron (Fe), magnesium (Mg),strontium (Sr), vanadium (V), a rare earth element, or a combinationthereof; D may be oxygen (O), fluorine (F), sulfur (S), phosphorus (P),or a combination thereof; E may be cobalt (Co), manganese (Mn), or acombination thereof; F may be fluorine (F), sulfur (S), phosphorus (P),or a combination thereof; G may be aluminum (Al), chromium (Cr),manganese (Mn), iron (Fe), magnesium (Mg), lanthanum (La), cerium (Ce),strontium (Sr), vanadium (V), or a combination thereof; Q may betitanium (Ti), molybdenum (Mo), manganese (Mn), or a combinationthereof; I′ may be chromium (Cr), vanadium (V), iron (Fe), scandium(Sc), yttrium (Y), or a combination thereof; and J may be vanadium (V),chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), ora combination thereof.

For example, the first positive active material may comprise a compoundrepresented by Formulae 17 to 19.

Li_(a)Ni_(b)CO_(c)Mn_(d)O₂  Formula 17

n Formula 17, 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, and 0≦d≦0.9.

Li₂MnO₃  Formula 18

LiMO₂  Formula 19

In Formula 19, M may be Mn, Fe, Co, or Ni.

Non-limiting examples of the conducting agent in the positive activematerial composition are carbon black, natural graphite, artificialgraphite, acetylene black, ketjen black, carbon fibers, carbonnanotubes; metallic materials, including copper, nickel, aluminum,silver, or the like, in powder, fiber, or tubular form; and conductivepolymers such as polyphenylene derivatives. Any suitable conductingagent available in the art may be used.

Non-limiting examples of the binder are a vinylidenefluoride/hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF),polyimide, polyethylene, polyester, polyacrylonitrile,polymethylmethacrylate, polytetrafluoroethylene (PTFE), a carboxymethylcellulose-styrene-butadiene rubber (SMC/SBR) copolymer, astyrene-butadiene rubber polymer, or a mixture thereof.

Non-limiting examples of the solvent include N-methyl-pyrrolidone (NMP),acetone, and water. Any suitable solvent available in the art may beused.

The amounts of the composite positive active material, the conductingagent, the binder, and the solvent may be determined by one of skill inthe art of manufacture of lithium batteries without undueexperimentation. At least one of the conducting agent, the binder, andthe solvent may be omitted depending on the use and the structure of thelithium battery.

A negative electrode of the lithium battery according to an embodimentmay be manufactured in substantially the same manner as in themanufacture of the positive electrode, except for using a negativeactive material instead of a positive active material.

The negative active material may be a carbonaceous material, silicon, asilicon oxide, a silicon-based alloy, a silicon-carbonaceous materialcomposite, tin, a tin-based alloy, a tin-carbon composite, a metaloxide, or a combination thereof.

The carbonaceous material may comprise crystalline carbon, amorphouscarbon, or a mixture thereof. The crystalline carbon may be graphite,such as natural graphite or artificial graphite that are in amorphous,plate, flake, spherical or fibrous form. The amorphous carbon may besoft carbon (carbon sintered at low temperatures), hard carbon,meso-phase pitch carbides, sintered cokes, graphene, carbon black,fullerene soot, carbon nanotubes, and carbon fibers. Any appropriatematerial available in the art may be used.

The negative active material may be selected from Si, SiO_(x) where0<x<2, for example, 0.5<x<1.5, Sn, SnO₂, a silicon-containing metalalloy, and a mixture thereof. The metal that is alloyable with siliconmay be at least one selected from Al, Sn, Ag, Fe, Bi, Mg, Zn, In, Ge,Pb, and Ti.

The negative active material may include a metal/metalloid alloyablewith lithium, an alloy thereof, or an oxide thereof. Examples of themetal/metalloid alloyable with lithium are Si, Sn, Al, Ge, Pb, Bi, Sb, aSi—Y′ alloy (where Y′ is an alkali metal, an alkaline earth metal, aGroup 13 element, a Group 14 element, a transition metal, a rare earthelement, or a combination thereof except for Si), a Sn—Y″ alloy (whereY″ is an alkali metal, an alkaline earth metal, a Group 13 element, aGroup 14 element, a transition metal, a rare earth element, or acombination thereof except for Sn), and MnO_(x) where 0<x≦2. Y′ and Y″may each independently be magnesium (Mg), calcium (Ca), strontium (Sr),barium (Ba), radium (Ra), scandium (Sc), yttrium (Y), titanium (Ti),zirconium (Zr), hafnium (Hf), rutherfordium (Rf), vanadium (V), niobium(Nb), tantalum (Ta), dubnium (Db), chromium (Cr), molybdenum (Mo),tungsten (W), seaborgium (Sg), technetium (Tc), rhenium (Re), bohrium(Bh), iron (Fe), lead (Pb), ruthenium (Ru), osmium (Os), hassium (Hs),rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), copper (Cu),silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), boron (B), aluminum(Al), gallium (Ga), tin (Sn), indium (In), germanium (Ge), phosphorus(P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S), selenium(Se), tellurium (Te), polonium (Po), or combinations thereof.Non-limiting examples of the oxide of the metal/metalloid alloyable withlithium are a lithium titanium oxide, a vanadium oxide, a lithiumvanadium oxide, SnO₂, and SiO_(x) where 0<x<2.

For example, the negative active material may include at least oneelement selected from the elements of Groups 13, 14, and 15 of thePeriodic Table of the Elements.

For example, the negative active material may include at least oneelement selected from Si, Ge, and Sn.

The amounts of the negative active material, the conducting agent, thebinder, and the solvent may be those levels as used in the manufactureof lithium batteries in the art. Examples of the conducting agent,binder, and solvent for the negative electrode may be the same as thoseused in the manufacture of the positive electrode.

A separator may be disposed between the positive electrode and thenegative electrode of the lithium battery. For example, the separatormay be an insulating thin film having high ion permeability and highmechanical strength.

The separator may have a pore diameter of about 0.005 μm to about 30 μm,about 0.01 μm to about 10 μm, or about 0.1 μm to about 5 μm, and athickness of about 1 μm to about 40 μm, about 5 μm to about 20 μm, orabout 8 μm to about 15 μm. Non-limiting examples of the separator areolefin-based polymers, such as polypropylene, and sheets or non-wovenfabric made of glass fiber or polyethylene. When a lithium batteryincludes a solid polymer electrolyte, the solid polymer electrolyte mayalso serve as the separator.

The separator may comprise a monolayer or a multilayer separatorincluding at least two layers of polyethylene, polypropylene,polyvinylidene fluoride, or a combination thereof. The multilayerseparator may be a mixed multilayer separator. For example, theseparator may be a two-layered separator including polyethylene andpolypropylene layers, a three-layered separator including polyethylene,polypropylene and polyethylene layers, or a three-layered separatorincluding polypropylene, polyethylene, and polypropylene layers.

The lithium salt-containing nonaqueous electrolyte may include anonaqueous electrolyte and a lithium salt.

The nonaqueous electrolyte may be a nonaqueous liquid electrolyte, anorganic solid electrolyte, or an inorganic solid electrolyte.

The nonaqueous liquid electrolyte may include an organic solvent. Theorganic solvent may be any suitable organic solvents available in theart. For example, the organic solvent may comprise at least one selectedfrom propylene carbonate, ethylene carbonate, fluoroethylene carbonate,butylene carbonate, dimethyl carbonate, diethyl carbonate, methylethylcarbonate, methylpropyl carbonate, ethylpropyl carbonate,methylisopropyl carbonate, dipropyl carbonate, dibutyl carbonate,chloroethylene carbonate, benzonitrile, acetonitrile, tetrahydrofuran,2-methyltetrahydrofuran, γ-butyrolactone, 1,3-dioxolane,4-methyl-1,3-dioxolane, N,N-dimethyl formamide, N,N-dimethyl acetamide,dimethylsulfoxide, dioxane, 1,2-dimethoxyethane, sulforane,dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, anddimethyl ether.

Non-limiting examples of the organic solid electrolyte are polyethylenederivatives, polyethylene oxide derivatives, polypropylene oxidederivatives, phosphoric acid ester polymer, polyester sulfide, polyvinylalcohol, polyvinylidene fluoride, and polymers includingionic-dissociative groups.

Non-limiting examples of the inorganic solid electrolyte are nitrides,halides, and sulfates of lithium, such as Li₃N, LiI, Li₅NI₂,Li₃N—LiI—LiOH, Li₂SiS₃, Li₄SiO₄, Li₄SiO₄—LiI—LiOH, and Li₃PO₄—Li₂S—SiS₂.

The lithium salt may be a material that is soluble in a non-aqueouselectrolyte, for example, LiPF₆, LiBF₄, LiSbF₆, LiAsF₆, LiCIO₄,LiCF₃SO₃, Li(CF₃SO₂)₂N, LiC₄F₉SO₃, LiAlO₂, LiAlCl₄,LiN(C_(x)F_(2x+1)SO₂)(C_(y)F_(2y+1)SO₂) where x and y are naturalnumbers, LiCl, LiI, or a mixture thereof. To improve charge-dischargecharacteristics and resistance to flame in the lithium battery,pyridine, triethylphosphate, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexamethyl phosphoramide, nitrobenzene derivative,sulfur, a quinone imine dye, N-substituted oxazolidinone,N,N-substituted imidazolidine, ethylene glycol dialkyl ether, anammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride may beadded to the nonaqueous electrolyte. In some embodiments, to providenonflammable characteristics, a halogen-containing solvent such ascarbon tetrachloride, ethylene trifluoride, or the like may be furtheradded to the nonaqueous electrolyte, if required.

Referring to FIG. 1, a lithium battery 11 according to an embodiment ofthe present disclosure may include a positive electrode 13, a negativeelectrode 12, and a separator 14. The positive electrode 13, thenegative electrode 12, and the separator 14 may be wound or folded, andthen sealed in a battery case 15. Subsequently, the battery case 15 maybe filled with an organic electrolyte and sealed with a cap assembly 16,thereby completing the manufacture of the lithium battery 11. Thebattery case 15 may be a cylindrical type, a rectangular type, or athin-film type. For example, the lithium battery 11 may be a thin filmtype battery. The lithium battery 11 may be a lithium ion battery.

In some embodiments, a bi-cell structure as a stack of two batteryassemblies may be formed and impregnated with an organic electrolyte.The resultant structure may then be put into a pouch and sealed, therebycompleting the manufacture of a lithium ion polymer battery.

In some other embodiments, a plurality of battery assemblies may bestacked upon one another to form a battery pack, which may be used inany devices that operate at high temperatures and require high output,for example, in a laptop computer, a smart phone, an electric vehicle,and the like.

A lithium battery according to any of the above-described embodimentsmay have improved high-rate characteristics and lifespancharacteristics, and thus may be applicable to an electric vehicle (EV),for example, in a hybrid vehicle such as a plug-in hybrid electricvehicle (PHEV).

An embodiment will now be described in further detail with reference tothe following examples. However, these examples are only forillustrative purposes and are not intended to limit the scope of thepresent disclosure.

EXAMPLES Preparation Example 1: Preparation of Composite Positive ActiveMaterial

A composite positive active material was synthesized using aco-precipitation method as follows.

A nickel sulfate, a cobalt sulfate, and a manganese sulfate as startingmaterials were stoichiometrically mixed together in order to prepare acomposite positive active material represented by the formulaLiNi_(0.85)Co_(0.10)Mn_(0.05)O₂.

The nickel sulfate, the cobalt sulfate, and the manganese sulfate weredissolved in distilled water to obtain a 2 molar (M) precursor mixture.After NH₄OH as a chelating agent and NaOH as a precipitating agent wereadded to the precursor mixture, continuous co-precipitation reaction wasperformed at a pH of about 11.5 and about 50° C. to obtain a precipitaterepresented by the formula Ni_(0.85)Co_(0.10)Mn_(0.05)(OH)₂.

This precipitate (Ni_(0.85)Co_(0.10)Mn_(0.05) (OH)₂) was washed withdistilled water and then dried at about 80° C. for about 24 hours. About50 grams (g) of the dried precipitate (Ni_(0.85)Co_(0.10)Mn_(0.05)(OH)₂)was mixed with 23.58 g of lithium hydroxide (LiOH.H₂O) and 2.71 g ofmanganese nitrate ((Mn(NO₃)₂.4H₂O). The resulting mixture was thermallytreated under oxygen atmosphere at about 750° C. for about 12 hours formelt-impregnation reaction, thus to obtain a composite positive activematerial represented by the formula0.98LiNi_(0.85)Co_(0.10)Mn_(0.05)O₂.0.02Li₂MnO₃.

Preparation Example 2: Preparation of Composite Positive Active Material

A composite positive active material represented by the formula0.95LiNi_(0.85)Co_(0.10)Mn_(0.05)O₂.0.05Li₂MnO₃ was prepared in the samemanner as in Preparation Example 1, except that the amounts of thenickel sulfate, cobalt sulfate, manganese sulfate, and manganese nitratewere appropriately varied to obtain the composite positive activematerial including about 5 mole percent (mol %) of Li₂MnO₃, based on atotal moles of the composite positive active material.

Preparation Example 3: Preparation of Composite Positive Active Material

A composite positive active material represented by the formula0.9LiNi_(0.85)Co_(0.10)Mn_(0.05)O₂.0.1Li₂MnO₃ was prepared in the samemanner as in Preparation Example 1, except that the amounts of thenickel sulfate, cobalt sulfate, manganese sulfate, and manganese nitratewere appropriately varied to obtain the composite positive activematerial including about 10 mol % of Li₂MnO₃.

Preparation Example 4: Preparation of Composite Positive Active Material

A composite positive active material represented by0.8LiNi_(0.85)Co_(0.10)Mn_(0.05)O₂.0.2Li₂MnO₃ was prepared in the samemanner as in Preparation Example 1, except that the amounts of thenickel sulfate, cobalt sulfate, manganese sulfate, and manganese nitratewere appropriately varied to obtain the composite positive activematerial including about 20 mol % of Li₂MnO₃.

Preparation Example 5: Preparation of Composite Positive Active Material

A composite positive active material represented by the formula0.98LiNi_(0.80)Co_(0.10)Mn_(0.10)O₂.0.02Li₂MnO₃ was prepared in the samemanner as in Preparation Example 1, except that the amounts of thenickel sulfate, cobalt sulfate, and manganese sulfate were varied in anappropriate stoichiometric ratio.

Preparation Example 6: Preparation of Composite Positive Active Material

A composite positive active material represented by0.98LiNi_(0.75)Co_(0.20)Mn_(0.05)O₂.0.02Li₂MnO₃ was prepared in the samemanner as in Preparation Example 1, except that the amounts of thenickel sulfate, cobalt sulfate, and manganese sulfate were varied in anappropriate stoichiometric ratio.

Preparation Example 7: Preparation of Composite Positive Active Material

A composite positive active material represented by0.98LiN_(i0.90)C_(o0.05)M_(n0.05)O₂.0.02L_(i2)MnO₃ was prepared in thesame manner as in Preparation Example 1, except that the amounts of thenickel sulfate, cobalt sulfate, and manganese sulfate were varied in anappropriate stoichiometric ratio.

Preparation Example 8: Preparation of Composite Positive Active Material

A composite positive active material represented by0.95LiNi_(0.80)Co_(0.10)Mn_(0.10)O₂.0.05Li₂MnO₃ was prepared in the samemanner as in Preparation Example 5, except that the amounts of thenickel sulfate, cobalt sulfate, manganese sulfate, and manganese nitratewere appropriately varied to obtain the composite positive activematerial including about 5 mol % of Li₂MnO₃.

Preparation Example 9: Preparation of Composite Positive Active Material

A composite positive active material represented by0.9LiNi_(0.80)Co_(0.10)Mn_(0.10)O₂.0.1Li₂MnO₃ was prepared in the samemanner as in Preparation Example 5, except that the amounts of thenickel sulfate, cobalt sulfate, manganese sulfate, and manganese nitratewere appropriately varied to obtain the composite positive activematerial including about 10 mol % of Li₂MnO₃.

Preparation Example 10: Preparation of Composite Positive ActiveMaterial

A composite positive active material represented by0.8LiNi_(0.80)Co_(0.10)Mn_(0.10)O₂.0.2Li₂MnO₃ was prepared in the samemanner as in Preparation Example 5, except that the amounts of thenickel sulfate, cobalt sulfate, manganese sulfate, and manganese nitratewere appropriately varied to obtain the composite positive activematerial including about 20 mol % of Li₂MnO₃.

Preparation Example 11: Preparation of Composite Positive ActiveMaterial

A composite positive active material represented by0.95LiNi_(0.75)Co_(0.20)Mn_(0.05)O₂.0.05Li₂MnO₃ was prepared in the samemanner as in Preparation Example 6, except that the amounts of thenickel sulfate, cobalt sulfate, manganese sulfate, and manganese nitratewere appropriately varied to obtain the composite positive activematerial including about 5 mol % of Li₂MnO₃.

Preparation Example 12: Preparation of Composite Positive ActiveMaterial

A composite positive active material represented by0.9LiNi_(0.75)Co_(0.20)Mn_(0.05)O₂.0.1Li₂MnO₃ was prepared in the samemanner as in Preparation Example 6, except that the amounts of thenickel sulfate, cobalt sulfate, manganese sulfate, and manganese nitratewere appropriately varied to obtain the composite positive activematerial including about 10 mol % of Li₂MnO₃.

Preparation Example 13: Preparation of Composite Positive ActiveMaterial

A composite positive active material represented by0.8LiNi_(0.75)Co_(0.20)Mn_(0.05)O₂.0.2Li₂MnO₃ was prepared in the samemanner as in Preparation Example 6, except that the amounts of thenickel sulfate, cobalt sulfate, manganese sulfate, and manganese nitratewere appropriately varied to obtain the composite positive activematerial including about 20 mol % of Li₂MnO₃.

Preparation Example 14: Preparation of Composite Positive ActiveMaterial

A composite positive active material represented by0.95LiNi_(0.90)Co_(0.05)Mn_(0.05)O₂.0.05Li₂MnO₃ was prepared in the samemanner as in Preparation Example 7, except that the amounts of thenickel sulfate, cobalt sulfate, manganese sulfate, and manganese nitratewere appropriately varied to obtain the composite positive activematerial including about 5 mol % of Li₂MnO₃.

Preparation Example 15: Preparation of Composite Positive ActiveMaterial

A composite positive active material represented by 0.9LiNi_(0.9)Co_(0.05)Mn_(0.05)O₂.0.1Li₂MnO₃ was prepared in the samemanner as in Preparation Example 7, except that the amounts of thenickel sulfate, cobalt sulfate, manganese sulfate, and manganese nitratewere appropriately varied to obtain the composite positive activematerial including about 10 mol % of Li₂MnO₃.

Preparation Example 16: Preparation of Composite Positive ActiveMaterial

A composite positive active material represented by0.8LiNi_(0.90)Co_(0.05)Mn_(0.05)O₂.0.2Li₂MnO₃ was prepared in the samemanner as in Preparation Example 7, except that the amounts of thenickel sulfate, cobalt sulfate, manganese sulfate, and manganese nitratewere appropriately varied to obtain the composite positive activematerial including about 20 mol % of Li₂MnO₃.

Preparation Example 17: Preparation of Composite Positive ActiveMaterial

A composite positive active material was prepared in the same manner asin Preparation Example 1, except that the precipitateNi_(0.85)Co_(0.10)Mn_(0.05) (OH)₂ was mixed with lithium hydroxide(LiOH.H₂O) and manganese acetate, instead of manganese nitrate(Mn(NO₃)₂.4H₂O).

Comparative Preparation Example 1: Preparation of Positive ActiveMaterial

A positive active material was synthesized using a co-precipitationmethod as follows.

A nickel sulfate, a cobalt sulfate, and a manganese sulfate as startingmaterials were stoichiometrically mixed together in order to prepare apositive active material represented by the formulaLiNi_(0.85)Co_(0.10)Mn_(0.05)O₂.

The nickel sulfate, the cobalt sulfate, and the manganese sulfate weredissolved in distilled water to obtain a 2M precursor mixture. AfterNH₄OH as a chelating agent and NaOH as a precipitating agent were addedto the precursor mixture, continuous co-precipitation reaction wasperformed at a pH of about 10.5 to about 12.5 and about 40° C. to 60° C.to obtain a precipitate represented by the formulaNi_(0.85)Co_(0.10)Mn_(0.05)(OH)₂.

This precipitate (Ni_(0.85)Co_(0.10)Mn_(0.05)(OH)₂) was washed withdistilled water and then dried at about 80° C. for about 24 hours. About50 g of the dried precipitate (Ni_(0.85)Co_(0.10)Mn_(0.05) (OH)₂) wasmixed with lithium hydroxide (LiOH.H₂O) in a stoichiometric ratio inorder to obtain the composite positive active material represented bythe formula LiNi_(0.85)Co_(0.10)Mn_(0.05)O₂.

The resulting mixture was thermally treated under oxygen atmosphere atabout 750° C. for about 12 hours to obtain the composite positive activematerial (LiNi_(0.85)Co_(0.10)Mn_(0.05)O₂) as a target product.

Comparative Preparation Example 2: Preparation of Mixture with PositiveActive Material

The positive active material (LiNi_(0.85)Co_(0.10)Mn_(0.05)O₂) preparedin Comparative Preparation Example 1 was mixed with Li₂MnO₃ in a moleratio of about 99.8:0.02 to obtain a mixture of the positive activematerial (LiNi_(0.85)Co_(0.10)Mn_(0.05)O₂) and Li₂MnO₃.

Comparative Preparation Example 3: Preparation of Composite PositiveActive Material

A composite positive active material represented by the formula0.98LiNi_(0.60)Co_(0.20)Mn_(0.20)O₂.0.02Li₂MnO₃ was prepared in the samemanner as in Preparation Example 1, except that the amounts of thenickel sulfate, cobalt sulfate, manganese sulfate, and manganese nitratewere appropriately varied to obtain the composite positive activematerial including about 2 mol % of Li₂MnO₃. Comparative PreparationExample 4: Preparation of composite positive active material

A composite positive active material represented by the formula0.7LiNi_(0.85)Co_(0.10)Mn_(0.05)O₂.0.3Li₂MnO₃ was prepared in the samemanner as in Preparation Example 1, except that the amounts of thenickel sulfate, cobalt sulfate, manganese sulfate, and manganese nitratewere appropriately varied to obtain the composite positive activematerial including about 30 mol % of Li₂MnO₃.

Example 1

A lithium battery was manufactured as follows using the compositepositive active material of Preparation Example 1. The compositepositive active material of Preparation Example 1, carbon as aconducting agent (Denka Black), and polyvinylidene fluoride (PVDF) as abinder were uniformly mixed in a weight ratio of about 90:5:5 in a NMPsolvent to prepare a slurry.

This slurry was then coated on an aluminum (Al) substrate (thickness: 15μm) using a doctor blade, dried at about 120° C. under reduced pressure,and then roll-pressed in sheet form, to thereby form a positiveelectrode.

The positive electrode and a lithium metal as a counter electrode wereassembled together, followed by injecting an electrolyte prepared bydissolving 1.3M LiPF₆ in a mixed solvent of ethylene carbonate (EC),ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) in a volumeratio of about 3:4:3.

Examples 2 to 17

Lithium batteries were manufactured in the same manner as in Example 1,except that the composite positive active materials of PreparationExamples 2 to 17, instead of the composite positive active material ofPreparation Example 1, were used, respectively.

Comparative Examples 1 to 4

Lithium batteries were manufactured in the same manner as in Example 1,except that the positive active materials of Comparative PreparationExamples 1 to 4, instead of the composite positive active material ofPreparation Example 1, were used, respectively.

Evaluation Example 1: X-Ray Diffraction Analysis

The composite positive active materials of Preparation Examples 1 to 4and the positive active material of Comparative Preparation Example 1were analyzed by X-ray diffraction (XRD) analysis using a RigakuRINT2200HF+ diffractometer with Cu—Kα radiation (1.540598 Å).

The X-ray diffraction analysis results are shown in FIGS. 2, 3, 4A and4B. FIG. 2 illustrates the results of the X-ray diffraction analysis onthe composite positive active materials of Preparation Examples 1 to 4and the positive active material of Comparative Preparation Example 1.FIGS. 3 and 4A are enlarged graphs of FIG. 2, illustrating the resultsof the X-ray diffraction at the (003) plane and at the (018) and (110)planes, respectively, in the composite active materials of PreparationExamples 1 to 4 and Comparative Preparation Example 1. FIG. 4B is anenlarged graph of FIG. 2 illustrating the results of the X-raydiffraction at the (110) plane in the composite positive active materialof Preparation Example 4.

Referring to FIGS. 2 and 3, in the composite positive active materialsof Preparation Examples 1 to 4, the larger the amount of Li₂MnO₃ became,the (003) peak was shifted more toward a low angle, with an increasedfull width at half maximum (FWHM) of the (003) plane peak, due to aneffect of the composite composition.

The FWHMs of the (003) plane peak in the composite positive activematerials of Preparation Examples 1 to 4 and the positive activematerial of Comparative Preparation Example 1 are shown in Table 1.

TABLE 1 Example 2theta (2θ, degree) FWHM (°) Preparation Example 118.7014 0.1968 Preparation Example 2 — 0.2165 Preparation Example 318.7034 0.2362 Preparation Example 4 18.7001 0.2362 ComparativePreparation 18.6931 0.1969 Example 1

Referring to Table 1, the composite positive active materials ofPreparation Examples 1, 3, and 4 were found to have a (003) plane peakthat was shifted more toward a low angle, compared to that of thepositive active material of Comparative Preparation Example 1. Thecomposite positive active materials of Preparation Examples 1 toPreparation Example 4 were found to have an increased FWHM of the (003)plane peak, compared to that of the positive active material ofComparative Preparation Example 1. Referring to FIG. 4A, the compositepositive active material of Preparation Example 4 including about 20mole % of Li₂MnO₃ was found to have a (110) plane peak of Li₂MnO₃appearing near about 20-25°.

Evaluation Example 2: Scanning Electron Microscopy (SEM)

The composite positive active materials of Preparation Examples 1 to 4and the positive active material of Comparative Preparation Example 1were analyzed by scanning electron microscopy (SEM).

The SEM results are shown in FIGS. 5A to 5E.

Referring to FIGS. 5A to 5E, the composite positive active materials ofPreparation Examples 1 to 4 were found to be not significantly differentin primary particle size, compared to the positive active material ofComparative Preparation Example 1 shown in FIG. 5E, and have a nearlysame primary particle size of about 300 nm. The primary particle sizerefers to a longer axis diameter of a particle.

Evaluation Example 3: Electron Probe Microanalysis (EPMA)

The composite positive active material of Preparation Example 3 and thepositive active material of Comparative Preparation Example 1 wereanalyzed using an electron probe microanalyzer (EPMA, JXA-8630F,available from JEOL) by which the atomic ratio was measured while movinga probe from the center of each sample toward the surface thereof.

FIGS. 6A to 6C illustrate the EPMA images of the composite activematerial of Preparation Example 3 as the results of measuring the atomicratio of nickel, cobalt and manganese while moving the probe of theelectron probe microanalyzer from the center of the composite positiveactive material of Preparation Example 3 to the surface thereof. Asshown in FIG. 6C, it is found that manganese originating from manganesenitrate may form a composite structure through melt impregnation intoparticles of the composite positive active material. FIGS. 7A to 7Cillustrate the EPMA images of the positive active material ofComparative Preparation Example 1 as the results of measuring the atomicratio of nickel, cobalt and manganese while moving the probe of theelectron probe microanalyzer from the center of the positive activematerial of Comparative Preparation Example 1 to the surface thereof.FIGS. 6D and 7D are cross-sectional SEM images of the composite positiveactive material of Preparation Example 3 and the positive activematerial of Comparative Preparation Example 1, respectively.

Evaluation Example 4: Evaluation of Residual Lithium Content

The amounts of residual lithium in the composite positive activematerials of Preparation Examples 1 to 3 and the positive activematerial of Comparative Preparation Examples 1, 2, and 4 were measuredusing the following method.

About 100 g of deionized water was added to 10 g of each sample and thenstirred at about 250 revolutions per minute (rpm) for about 30 minutes,followed by filtration and titration with a 0.1M HCl aqueous solution.Two inflection points appear after the titration, as shown in FIG. 9,wherein the amount of residual lithium was calculated based on the addedamounts of the HCl aqueous solution at the two inflection points.

The amounts of LiOH and Li₂CO₃ measured according to the above-describedmethod are shown in Table 2 and FIG. 8.

TABLE 2 Amount of Amount of Li₂MnO₃ Li₂CO₃ Amount of LiOH Free LiExample content (wt %) (wt %) (ppm) Preparation x = 0.02 0.591 0.86614,571 Example 1 Preparation x = 0.05 0.537 0.801 13.382 Example 2Preparation x = 0.10 0.535 0.446 9,810 Example 3 Comparative x = 0.001.372 0.918 22,899 Preparation Example 1

Referring to Table 2 and FIG. 8, the composite positive active materialsof Preparation Examples 1 to 3 were found to have a smaller amount ofresidual lithium than that of the positive active material ofComparative Preparation Example 1, indicating a significant reduction inthe amount of lithium carbonate in the surface of the composite positiveactive materials of Preparation Examples 1 to 3.

The results of measuring the amounts of residual lithium in the positiveactive materials of Comparative Preparation Examples 2 and 4 are asfollows.

As a result of measuring the amount of residual lithium in the positiveactive material of Comparative Preparation Example 4, the positiveactive material of Comparative Preparation Example 4 had an equivalentamount of residual lithium to that of the composite positive activematerial of Preparation Example 1.

The positive active materials of Comparative Preparation Examples 2 and4 had nearly the same or similar amount of residual lithium as that ofthe positive active material of Comparative Preparation Example 1.

As a result of measuring the amount of residual lithium in the compositepositive active material of Preparation Example 17, the compositepositive active material of Preparation Example 17 had an equivalentamount of residual lithium to that of the composite positive activematerial of Preparation Example 1.

Evaluation Example 5: Charge-Discharge Characteristics

Charge-discharge characteristics of the lithium batteries of Examples 1to 4 and Comparative Examples 1 to 4 were evaluated after a firstcharging and discharging cycle, a second charging and discharging cycle,and repeated (cyclic) charging and discharging at about 25° C.

Each of the lithium batteries of Examples 1 to 4 and Comparative Example1 was charged with a constant current of 0.1 C to about 4.7V and thendischarged with a constant current of 0.1 C to about 2.5V (First cycle),and was charged, from the second cycle, in a constant current andconstant voltage (CC/CV) mode at 0.5 C and 4.6V, and then discharged at0.2 C/1 C/2 C to 2.5V. This charging and discharging cycle was repeated50 times, wherein charging with a constant current of 1 C to 4.6V wasfollowed by discharging with 1 C to 2.5V.

The C rate for current means a current which will discharge a battery inone hour, e.g., a C rate for a battery having a discharge capacity of1.6 ampere-hours would be 1.6 amperes.

The initial efficiency, rate capability, discharge voltage decay, andcapacity retention rate of a lithium battery are defined by Equations 1to 4, respectively. An initial discharge capacity refers to a dischargecapacity after 1^(st) cycle of charging and discharging.

Initial efficiency={(1^(st) cycle discharge capacity)/(1^(st) cyclecharge capacity)}×100%  Equation 1

Rate capability={(2 C Discharge capacity)/(0.2 C Dischargecapacity)}×100%  Equation 2

Discharge voltage decay[mV]=[50^(th) cycle average dischargevoltage−1^(st) cycle average discharge voltage]  Equation 3

In Equation 3, the average discharge voltage refers to a dischargevoltage corresponding to an intermediate level of the discharge voltageat each cycle.

Capacity retention rate[%]=[50^(th) cycle discharge capacity/1^(st)cycle discharge capacity]×100%  Equation 4

The results of evaluating the charge-discharge characteristics of thelithium batteries of Examples 1 to 4 and Comparative Example 1, initialefficiencies and rate capabilities of the lithium batteries are shown inTable 3. The results of evaluating the charge-discharge characteristicsof the lithium batteries of Examples 1 to 6 and Comparative Examples 1and 3, capacity retention rates and discharge voltage decays of thelithium batteries are shown in Table 4. A discharge voltage decay refersto a difference between the discharge voltage after 50^(th) cycle andthe discharge voltage after 1^(st) cycle.

TABLE 3 1^(st) cycle 0.1 C Initial 0.1 C Charge Discharge efficiencyRate capability Example capacity capacity (%) 2 C/0.2 C (%) Example 1235 225 95.9 90.6 Example 2 221 211 95.2 89.4 Example 3 211 199 94.487.0 Example 4 195 178 91.1 88.0 Comparative 240 230 95.8 91.4 Example 1

TABLE 4 Discharge voltage Lifetime Average voltage (V) decay (Δ)(50^(th) cycle) Example After 1^(st) cycle After 50^(th) cycle (mV) (%)Example 1 3.821 3.795 −25 91.9 Example 2 3.829 3.808 −22 96.0 Example 33.826 3.807 −18 95.5 Example 4 3.831 3.808 −23 92.5 Comparative 3.8283.788 −40 91.0 Example 1

Referring to Table 3, the lithium batteries of Examples 1 to 4, eachhaving a positive electrode including a Li₂MnO₃-containing compositepositive active material, were found to be slightly lower in initialefficiency and rate capability, compared to those of the lithium batteryof Comparative Preparation Example 1.

Referring to Table 4, the lithium batteries of Examples 1 to 4 exhibitedimproved lifetime characteristics and an improvement in dischargevoltage decay, compared to those of the lithium battery of ComparativeExample 1.

As a result of evaluating lifetime characteristics and discharge voltagedecay, the lithium battery of Comparative Example 2 was found to bepoorer in lifetime characteristics and discharge voltage decay, comparedto those of the lithium batteries of Examples 2 to 4.

The lithium batteries of Comparative Examples 3 and 4 had reducedoverall cell performance, including discharge capacity, compared to thatof the lithium batteries of Examples 1 to 3.

As described above, according to the one or more embodiments, acomposite positive active material including a first metal oxide ofFormula 1 and a second metal oxide may have a reduced amount of lithiumand suppress a side reaction during charging and discharging, thusimproving structural stability of a lithium battery. A high power-outputand high-capacity lithium battery having improved lifetimecharacteristics and a reduced discharge voltage decay even underrepeated charging and discharging may be manufactured using a positiveelectrode including the composite positive active material.

It should be understood that embodiments described herein should beconsidered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould be considered as available for other similar features or aspectsin other embodiments.

While an embodiment has been described with reference to the figures, itwill be understood by those of ordinary skill in the art that variouschanges in form and details may be made therein without departing fromthe spirit and scope of the disclosure.

What is claimed is:
 1. A composite positive active material comprising:a composite comprising a first metal oxide represented by Formula 1 andhaving a layered structure, and a second metal oxide having at least onecrystal structure selected from a layered structure, a perovskitestructure, a rock salt structure, and a spinel structure; wherein acontent of the second metal oxide is greater than 0 and equal to or lessthan 0.2 moles, per mole of the composite,LiNi_(x)M¹ _(1-x)O_(2-e)M^(a) _(e)  Formula 1 wherein, in Formula 1, M¹is at least one element selected from Group 4 to Group 14 element of thePeriodic Table of the Elements; M^(a) is at least one element selectedfrom F, S, Cl, and Br 0.7≦x<1; and 0≦e<1.
 2. The composite positiveactive material of claim 1, wherein an amount of residual lithium in thecomposite positive active material is about 15,000 parts per million orless, based on a total amount of the composite positive active material.3. The composite positive active material of claim 1, wherein M¹ inFormula 1 comprises at least one metal selected from manganese,vanadium, chromium, iron, cobalt, nickel, zirconium, rhenium, aluminum,boron, germanium, ruthenium, tin, titanium, niobium, molybdenum, andplatinum.
 4. The composite positive active material of claim 1, whereinthe first metal oxide of Formula 1 is a compound represented by Formula2,LiNi_(x)Co_(y)Mn_(z)M³ _(c)O_(2-e)M^(a) _(e)  Formula 2 wherein, inFormula 2, 0.7≦x≦0.99; 0≦y<1; 0<z<1; 0≦c<1; 0<x+y+z+c≦1; 0≦e<1; M³ is atleast one selected from Group 4 to Group 14 elements of the PeriodicTable of the Elements; and M^(a) is at least one element selected fromF, S, Cl, and Br.
 5. The composite positive active material of claim 1,wherein the first metal oxide of Formula 1 is a compound represented byFormula 3:LiNi_(x)Co_(y)Mn_(z)O₂  Formula 3 wherein, in Formula 3, 0.7≦x≦0.99;0<y<1; 0<z<1; and 0<x+y+z≦1.
 6. The composite positive active materialof claim 1, wherein the second metal oxide is a compound represented byFormula 4, a compound represented by Formula 5, a compound representedby Formula 6, or a compound represented by Formula 7,A₂M²O₃,  Formula 4AM²O₃,  Formula 5(A_(b)M² _(1-b))O, or  Formula 6AM² ₂O₄,  Formula 7 wherein, in Formulae 4 to 7, A is at least oneelement selected from Group 1 to Group 3 elements of the Periodic Tableof the Elements, M² is at least one element selected from Group 2 toGroup 16 elements and rare earth elements, and 0≦b≦1.
 7. The compositepositive active material of claim 6, wherein, in Formulae 4 to 7, A isat least one element selected from Li, Na, La, Sr, Ba, H, K, Ca, and Y;and M² is at least one element selected from Al, Ga, Ge, Mg, Nb, Zn, Cd,Ti, Co, Ni, Mn, Ca, Si, Fe, Cu, Sn, V, B, P, Se, Bi, As, Zr, Re, Ru, Cr,Sr, Sc, and Y.
 8. The composite positive active material of claim 6,wherein the compound represented by Formula 4 is Li₂MnO₃, Li₂TiO₃,Li₂SnO₃, Li₂ZrO₃, Li₂MoO₃, or Li₂RuO₃.
 9. The composite positive activematerial of claim 6, wherein the compound represented by Formula 5 is acompound represented by Formula 8,(A¹ _(1-a)A² _(a))M¹O₃  Formula 8 wherein, in Formula 8, A¹ is at leastone selected from La, Sr, Ba, Ce, Y, and Sc; A² is at least one selectedfrom Li, Na, Ca, Ag, K, Mg, and Cu; M¹ is at least one selected from Mn,V, Cr, Fe, Co, Ni, Zr, Ti, Mg, Cu, Nb, Ta, Ru, W, and Sn; and 0<a≦0.3.10. The composite positive active material of claim 6, wherein thecompound represented by Formula 6 is at least one selected from(Li_(b)Ni_(1-b))O, (Li_(b)Co_(1-b))O, (Li_(b)Fe_(1-b))O,(Li_(b)Cu_(1-b)O, (Li_(b)Zn_(1-b))O, (Li_(b)Ca_(1-b))O,(Li_(b)Sr_(1-b))O, (Li_(b)Mg_(1-b))O, and (Li_(b)Cr_(1-b))O), whereineach b is independently selected and is 0≦b≦1.
 11. The compositepositive active material of claim 6, wherein the compound represented byFormula 7 is LiMn₂O₄, LiNi_(0.5)Mn_(1.5)O₄, LiCo_(0.5)Mn_(1.5)O₄,Li[Co_(f)Ni_(g)Mn_(h)]₂O₄, or Li[Cu_(c)Mn_(2-c)]₂O₄, wherein 0<c≦2,0<f≦2; 0<g≦2, 0<h≦2; and f+g+h=2.
 12. The composite positive activematerial of claim 1, wherein the composite positive active materialcomprises at least one selected from compounds represented by Formulae 9to 12,(1−a)LiNi_(x)M¹ _(1-x)O₂ .aA₂M²O₃,  Formula 9(1−a)LiNi_(x)M¹ _(1-x)O₂ .aAM²O₃,  Formula 10(1−a)LiNi_(x)M¹ _(1-x)O₂ .a(A_(b)M² _(1-b))O, and  Formula 11(1−a)LiNi_(x)M¹ _(1-x)O₂ .aAM² ₂O₄,  Formula 12 wherein, in Formulae 9to 12, A is at least one metal selected from Li, Na, La, Sr, Ba, H, K,Ca, and Y; M² is at least one selected from Al, Ga, Ge, Mg, Nb, Zn, Cd,Ti, Co, Ni, Mn, Ca, Si, Fe, Cu, Sn, V, B, P, Se, Bi, As, Zr, Re, Ru, Cr,Sr, Sc, Y, and a rare earth element; and 0<a≦0.2, 0<b≦1.
 13. Thecomposite positive active material of claim 1, wherein the compositepositive active material is at least one selected from compoundsrepresented by Formulae 9-1 to 12-1,(1−a)LiNi_(x)Co_(y)Mn_(z)O₂ .aLi₂MnO₃,  Formula 9-1(1−a)LiNi_(x)Co_(y)Mn_(z)O₂ .aLiMnO₃,  Formula 10-1(1−a)LiNi_(x)Co_(y)Mn_(z)O₂ .a(Li_(b)La_(1-b))MnO₃,  Formula 10-2(1−a)LiNi_(x)Co_(y)Mn_(z)O₂ .a(Li_(b)Ni_(1-b))O, and  Formula 11-1(1−a)LiNi_(x)Co_(y)Mn_(z)O₂ .aLiMn₂O₄,  Formula 12-1 wherein, inFormulae 9-1 to 12-1, 0.7≦x≦0.99, 0<y≦0.3, 0<z≦0.3, x+y+z=1, 0<b≦1, and0<a≦0.2.
 14. The composite positive active material of claim 13,wherein, in Formulae 9-1 to 12-1, LiNi_(x)Co_(y)Mn_(z)O₂ is selectedfrom LiNi_(0.85)Co_(0.10)Mn_(0.05)O₂, LiNi_(0.8)Co_(0.1)Mn_(0.1)O₂,LiNi_(0.75)Co_(0.20)Mn_(0.05)O₂, and LiNi_(0.9)Co_(0.05)Mn_(0.05)O₂. 15.The composite positive active material of claim 1, wherein the secondmetal oxide is intermixed in the layered structure of the first metaloxide.
 16. The composite positive active material of claim 1, whereinthe composite positive active material is selected from0.98LiNi_(0.85)Co_(0.10)Mn_(0.05)O₂.0.02Li₂MnO₃,0.95LiNi_(0.85)Co_(0.10)Mn_(0.05)O₂.0.05Li₂MnO₃,0.9LiNi_(0.85)Co_(0.10)Mn_(0.05)O₂.0.1Li₂MnO₃,0.8LiNi_(0.85)Co_(0.10)Mn_(0.05)O₂.0.2Li₂MnO₃,0.98LiNi_(0.8)Co_(0.1)Mn_(0.1)O₂.0.02Li₂MnO₃,0.95LiNi_(0.8)Co_(0.1)Mn_(0.1)O₂.0.05Li₂MnO₃,0.9LiNi_(0.8)Co_(0.1)Mn_(0.1)O₂.0.1Li₂MnO₃,0.8LiNi_(0.8)Co_(0.1)Mn_(0.1)MnO₂.0.2Li₂MnO₃,0.98LiNi_(0.75)Co_(0.20)Mn_(0.05)O₂.0.02Li₂MnO₃,0.95LiNi_(0.75)Co_(0.20)Mn_(0.05)O₂.0.05Li₂MnO₃,0.9LiNi_(0.75)Co_(0.20)Mn_(0.05)O₂.0.1Li₂MnO₃,0.8LiNi_(0.75)Co_(0.20)Mn_(0.05)O₂.0.2Li₂MnO₃,0.98LiNi_(0.9)Co_(0.05)Mn_(0.05)O₂.0.02Li₂MnO₃,0.95LiNi_(0.9)Co_(0.05)Mn_(0.05)O₂.0.05Li₂MnO₃,0.9LiNi_(0.9)Co_(0.05)Mn_(0.05)O₂.0.1Li₂MnO₃, and0.8LiNi_(0.8)Co_(0.05)Mn_(0.05)O₂.0.2Li₂MnO₃.
 17. The composite positiveactive material of claim 1, wherein, when evaluated by X-ray diffractionanalysis with Cu—Kα radiation, a diffraction peak measured at a 2 thetavalue of about 18.5° to about 19.0° has a full width at half maximum ofabout 0.1968° to about 0.2362°.
 18. The composite positive activematerial of claim 1, wherein a half cell having a positive elementincluding the composite positive active material and lithium metal as acounter electrode has an average discharge voltage of about 92.5% toabout 99.95% after a 50^(th) charging and discharging cycle, withrespect to the average discharge voltage after a 1^(st) charging anddischarging cycle.
 19. The composite positive active material of claim1, wherein the composite positive active material has a surfacecomprising the second metal oxide.
 20. The composite positive activematerial of claim 1, wherein the composite positive active materialfurther comprises a coating layer on a surface thereof, and wherein thecoating layer comprises at least one selected from a conductivematerial, a metal oxide, and an inorganic fluoride.
 21. The compositepositive active material of claim 20, wherein the conductive material isat least one selected from a carbonaceous material, indium tin oxide,RuO₂, and ZnO.
 22. The composite positive active material of claim 20,wherein the metal oxide is at least one selected from silica, alumina,zirconium oxide, and titanium oxide.
 23. The composite positive activematerial of claim 20, wherein the coating layer comprises an inorganicfluoride, and wherein the inorganic fluoride is at least one selectedfrom AlF₃, CsF, KF, LiF, NaF, RbF, TiF, AgF, AgF₂, BaF₂, CaF₂, CuF₂,CdF₂, FeF₂, HgF₂, Hg₂F₂, MnF₂, MgF₂, NiF₂, PbF₂, SnF₂, SrF₂, XeF₂, ZnF₂,AlF₃, BF₃, BiF₃, CeF₃, CrF₃, DyF₃, EuF₃, GaF₃, GdF₃, Fe_(F3), HoF₃,InF₃, LaF₃, LuF₃, MnF₃, NdF₃, VOF₃, PrF₃, SbF₃, ScF₃, SmF₃, TbF₃, TiF₃,TmF₃, YF₃, YbF₃, TlF₃, CeF₄, GeF₄, HfF₄, SiF₄, SnF₄, TiF₄, VF₄, ZrF₄,NbF₅, SbF₅, TaF₅, BiF₅, MoF₆, ReF₆, SF₆, and WF₆.
 24. A method ofpreparing the composite positive active material of claim 1, the methodcomprising: mixing a first metal oxide precursor represented by Formula13, a lithium precursor, and a manganese precursor to prepare acomposition for forming a composite positive active material; andthermally treating the composition for forming the composite positiveactive material to prepare the composite positive active material ofclaim 1,Ni_(x)M¹ _(1-x)Q  Formula 13 wherein, in Formula 13, M¹ is at least oneelement selected from Group 4 to Group 14 of the Periodic Table of theElements; Q is OH, CO₃, or —(C₂O₄); and 0.7≦x<1.
 25. The method of claim24, wherein the manganese precursor is at least one selected frommanganese nitrate and manganese acetate.
 26. The method of claim 24,wherein the first metal oxide precursor represented by Formula 13 is acompound represented by Formula 14:Ni_(x)Co_(y)Mn_(z)M³ _(c)OH  Formula 14 wherein, in Formula 14, 0.7≦x<1;0<y≦0.3; 0<z≦0.3; 0≦c≦0.3; x+y+z+c=1; and M³ is at least one elementselected from Group 4 to Group 14 elements of the Periodic Table of theElements.
 27. The method of claim 26, wherein the compound representedby Formula 13b is a compound represented by Formula 15,Ni_(x)Co_(y)Mn_(z)OH  Formula 15 wherein, in Formula 15, 0.7≦x≦0.99;0≦y≦0.3; 0≦z≦0.3; and x+y+z=1.
 28. The method of claim 27, wherein thecompound represented by Formula 14 is selected fromLiNi_(0.85)Co_(0.10)Mn_(0.05)OH, LiNi_(0.8)Co_(0.1)Mn_(0.1)OH,LiNi_(0.75)Co_(0.20)Mn_(0.05)OH, and LiNi_(0.9)Co_(0.05)Mn_(0.05)OH. 29.The method of claim 26, wherein the thermal treating is performed at atemperature of about 700° C. to about 1000° C.
 30. The method of claim24, wherein the method further comprises adding an anion doping materialto the composite positive active material forming composition before thethermal treating.
 31. A positive electrode comprising the compositepositive active material of claim
 1. 32. A lithium battery comprisingthe positive electrode of claim 31.